A good seasoning rub for prime rib includes 1/4 cup each of black and coarse ground pepper, salt, garlic powder and onion powder; 2 tablespoons paprika, 2 tablespoons seasoning salt and 1 tablespoon celery salt. Adding 2 tablespoons of meat tenderizer is optional.
Combine all of the ingredients in a bowl, and spread into the meat, using the ratio of approximately 1/2 cup of seasoning to 10 pounds of meat. Add some soy sauce when rubbing the mixture into the meat. After rubbing in the mixture very well, place the seasoned meat in the refrigerator for 24 hours before cooking.
When ready to cook, place the seasoned meat on a bed of sliced raw onions in a large pan. Place the pan in an oven heated to 350 degrees Fahrenheit for approximately two hours, depending on the meat's weight.